1. Field of the Invention
This invention relates to a circuit for computing and controlling the power supplied to an alternating current motor especially suited for use with an alternating current linear induction motor.
2. Description of the Prior Art
The motor control art is quite advanced in certain of its aspects. Controlled rectifier bridges are well-known and understood for motor control applications. Trigger logic required in conjunction with such controlled rectifier bridges is also highly developed. It is commonplace to provide controlled slip operation of an induction motor, using generally known trigger logic circuit designs to gate controlled rectifiers in a controlled rectifier bridge to supply variable voltage-variable frequency power to the motor. It is likewise within the state of the art to develop continuously varying reference control signals correlated with the operating frequency of the controlled rectifier bridge. Providing specific circuits to achieve these control functions and related motor control functions is readily within the skill of the motor circuit designer, so too for the broad circuit design requirements of closed loop control systems using these various circuits.
Techniques are known in the prior art for regulating the frequency and voltage of a controlled rectifier bridge supplying an alternating current motor to provide motor control in relation to speed, torque and other motor operating parameters. Central to these prior art motor control systems is a mechanical, or electromechanical, measurement of the operating parameter providing the basis for control. For example, to control applied power in relation to motor speed, a mechanical, or electro-mechanical, tachometer is normally used to monitor motor speed. Similarly, when torque is the pertinent control parameter, sensing devices, such as strain gauges, are required to monitor motor operation.